It has been hitherto known as a method of automatically conveying various loads along a specified route to mount the load on a carriage and tow this carriage along a specified route by an unattended driving vehicle.
For such a conveying carriage, a carriage free to move on the floor is used, and a route is determined by a lead wire buried in the floor, or a display line such as metallic tape glued on the floor. These are detected by a magnetic or optical detecting means built into the driving vehicle. The vehicle is designed to convey along a specified route by steering the wheels of the driving vehicle, which is known as a carriage conveying apparatus having flexibility.
Also known is a carriage conveying apparatus enhanced in space usage efficiency by designing it to tow with the driving vehicle positioned under the carriage to be conveyed.
In such a method of towing the carriage with a driving vehicle, however, since the tractive force is obtained by frictional force between the driving wheels of the driving vehicle and the floor, the driving wheels may slip if the weight of the driving vehicle is light, making it impossible to travel, and therefore the live load on the carriage is limited, and accordingly, the weight of the driving vehicle itself must be increased.
When a carriage to be conveyed is coupled behind the driving vehicle, a wide space is needed for a coupling and decoupling station of the driving vehicle and the conveyed carriage, or for their stopping area and for the curved portion of the conveying route.
On the other hand, in the conventional driving vehicle getting under the conveyed carriage, as the driving vehicle can move only back and forth in the running direction, it is impossible to couple the two unless the conveyed carriage is correctly placed on the route of the driving vehicle.
In either method, furthermore, it is impossible to slide, spin or turn the carriage to be conveyed, and handling of the carriage is difficult at the station or load handling point.